Color registration apparatus and method, image forming apparatus employing the same apparatus, and image output method of the image forming apparatus

Abstract

A color registration apparatus that independently forms images of predetermined respective colors and compensates a mis-registration between the overlapped images of respective colors employed in an image forming apparatus of forming a color image by overlapping the images of respective colors, includes a detecting unit to detect a contour form and positional information of respective color patterns formed on an image transfer path by the image forming apparatus proportional to a corresponding format of a printing medium where the color image will be transferred, and a controller to compensate a mis-registration between the overlapped images of respective colors through based on data detected by the detecting unit.

1. A color registration apparatus to independently form images of predetermined respective colors and to compensate a mis-registration between overlapped images of respective colors employed in an image forming apparatus, comprising:
 a detecting unit to detect contour form and position information of respective test patterns for each color image formed on an image transfer path by the image forming apparatus proportional to a corresponding format of a printing medium where a color image will be transferred; and 
 a controller to compensate a mis-registration between the overlapped images of respective colors based on data detected by the detecting unit, 
 wherein each test pattern comprises a first edge corresponding to a top edge part of the printing medium and a second edge corresponding to one side edge of the printing medium. 
 
     
     
       2. The color registration apparatus of  claim 1 , wherein the detecting unit comprises:
 a light source to radiate a light; and 
 a plurality of light receiving elements aligned to have a length larger than a maximum width of the printing medium permitted by the image forming apparatus, the plurality of light receiving elements extending across the image transfer path in a width direction of the test patterns, and 
 wherein interference of each test pattern is detected by the plurality of light receiving elements to determine a contour form of the printing medium, a skew quantity and a shift quantity of each test pattern. 
 
     
     
       3. The color registration apparatus of  claim 2 , wherein the color patterns are separately formed on opposite side edges along the image transfer path; and
 the detecting unit includes two spaced apart sub-units separately formed and positioned to correspond with the separated test patterns on the opposite side edges along the image transfer path. 
 
     
     
       4. The color registration apparatus of  claim 2 , wherein the plurality of light receiving elements have a same size and are separated from each other by a constant interval. 
     
     
       5. The color registration apparatus of  claim 1 , further comprising a discriminating unit which discriminates whether there is a mis-registration and an extent of the mis-registration based on the data detected by the detecting unit. 
     
     
       6. The color registration apparatus of  claim 5 , wherein the discriminating unit comprises:
 a memory to store the contour form information of the respective test patterns; and 
 a counter to calculate a transfer time between the respective test patterns, and 
 wherein the discriminating unit determines the color registration between the respective test patterns through comparing information of the respective test patterns detected by the detecting unit and the counter and information of the respective test patterns stored in the memory. 
 
     
     
       7. The color registration apparatus of  claim 6 , wherein each test pattern comprises:
 a first test pattern corresponding to a leading edge and opposites side edges at the leading edge of the printing medium; and 
 a second test pattern corresponding to a trailing edge and opposites side edges at the trailing edge of the printing medium. 
 
     
     
       8. A method of a color registration that independently forms images of predetermined respective colors and compensate a mis-registration between overlapped images of respective colors employed in an image forming apparatus which forms a color image by overlapping images of respective colors, the method comprising:
 forming respective test patterns for each color image on an image transfer path proportional to a corresponding a format of a printing medium where the color image will be transferred; 
 detecting contour form information of each test pattern; and 
 compensating the color mis-registration based on the detected contour form information of the fed printing medium, 
 wherein the detecting of the contour form of each test pattern comprises: 
 radiating a light; 
 receiving the radiated light by a plurality of light receiving elements which are aligned to have a length longer than a maximum width of the printing medium permitted by the image forming apparatus, the plurality of light receiving elements extending across an image transfer path of the printing medium; 
 at predetermined times during an existence of the respective test patterns, outputting a signal corresponding to the radiated light received by the plurality of light receiving elements; and 
 recognizing the contour form of the respective test patterns using the output signal. 
 
     
     
       9. The method of the color registration of  claim 8 , further comprising determining whether there is a mis-registration and an extent of the mis-registration based on the contour form of the respective test patterns. 
     
     
       10. The method of the color registration of  claim 9 , wherein determining whether there is a mis-registration comprises
 determining sizes of the respective test patterns; 
 determining skew quantities of the respective test patterns; and 
 determining shift quantities of the respective test patterns. 
 
     
     
       11. The method of the color registration of  claim 10 , wherein determining the sizes of the respective test patterns comprises:
 calculating widths of the respective test patterns using an arithmetic operation having as variables a pass time of the respective test patterns, a location of individual light receiving elements of the detecting unit and a predetermined moving speed of the image transfer path. 
 
     
     
       12. The method of the color registration of  claim 11 , wherein the determining the sizes of the respective test patterns comprises:
 determining a moving direction of the respective test patterns; 
 calculating widths of the respective test patterns with the output signal; 
 storing formats of the respective test patterns; and 
 comparing the widths of the respective test patterns and preset formats. 
 
     
     
       13. The method of the color registration of  claim 12 , wherein calculating the widths of the respective test patterns with the output signal satisfies the following equations:
     P   width   =√X   2   +Y   2    
     X =ABS( i   —   ccw−i   —   cw )×( w+d )+ m  
 
     Y=f×V×T    
 where, for the respective test pattern, ABS means absolute value of, i_cw is an index number of the light receiving element disposed at a location which first meets a vertex of the respective test pattern and i_ccw is an index number of the light receiving element disposed at a location which meets an opposite vertex of the respective test pattern, w is the width of the light receiving element, d is a width of the interval between the light receiving elements, m is a margin that compensates to consider when the edge of each test pattern covers one light receiving element or the interval, f is a number of counts counted during an entering of the test pattern from the first entering of a vertex of the test pattern till the last entering of the other vertex of the test pattern, V is a moving speed of each test pattern, and T is a detecting period of the light receiving element. 
 
     
     
       14. The method of the color registration of  claim 10 , wherein the plurality of light receiving elements are separated from their adjacent light receiving elements by a predetermined interval, and
 determining the sizes of the respective test patterns further comprises determining the position of at least one vertex of a leading edge of the respective test pattern within an interval between the adjacent light receiving elements when the at least one vertex of the respective test pattern enters the interval between the adjacent light receiving elements. 
 
     
     
       15. The method of the color registration of  claim 14 , wherein determining the position of at least one vertex of a leading edge of the respective test patterns within an interval between the adjacent light receiving elements comprises:
 storing a relationship of a skew quantity and an output pattern of a transition of an output of the light receiving elements in a lookup table; 
 periodically storing sensed output values of the light receiving elements; 
 determining the skew quantity using the sensed output values of the light receiving elements and the relationship stored in the lookup table; 
 calculating a first line extending along the leading edge of each test pattern and a second line extending along a side edge of each test pattern; and 
 calculating the position of the at least one vertex of the leading edge of each test pattern from an intersection point of the first line and the second line. 
 
     
     
       16. The method of the color registration of  claim 10 , wherein determining the skew quantities of the respective test patterns comprises for each test pattern:
 storing a count counted from a time when the test pattern is first detected until two opposite side edges of the test pattern is detected; 
 deciding whether the test pattern is skewed according to which light receiving element among the plurality of light receiving elements first detects the respective test patterns; 
 storing index values of the light receiving elements disposed at locations which first meet the first two vertexes of the test pattern; and 
 calculating the skew quantity based on the count and the stored index values. 
 
     
     
       17. The method of the color registration of  claim 16 , wherein, the skew quantities are determined in accordance with the following equations:
   Skew quantity=arctan( Y/X ) 
     X =ABS( i   —   cw−i   —   ccw )×( w+d )+ m  
 
     Y=f×V×T    
 where, for the respective test pattern, ABS means absolute value of, i_cw is an index number of the light receiving element disposed at a location which first meets a vertex of the test pattern and i_ccw is an index number of the light receiving element disposed at a location which meets the opposite vertex of the test pattern, w is the width of the light receiving element, d is a width of the interval between the light receiving elements, m is a margin that compensates to consider when the edges of the respective test patterns cover one light receiving element or the interval, f is a number of counts counted during an entering of the test pattern from the first entering of a vertex of the test pattern till the last entering of the other vertex of the test pattern, V is a moving speed of the respective test patterns, and T is a detecting period of the light receiving element. 
 
     
     
       18. The method of the color registration of  claim 17 , wherein determining the skew quantities of the respective test patterns further comprises:
 determining whether the skew quantities continue to change while continuing to transfer the respective test patterns; and 
 estimating the skew quantities at a predetermined target location if the skew quantities are determined to continue to change. 
 
     
     
       19. The method of the color registration of  claim 10 , wherein determining the shift quantities of the respective test patterns comprises:
 determining which light receiving elements among the plurality of the light receiving elements are located at left and right portions of the leading edge of the respective test pattern. 
 
     
     
       20. The method of the color registration of  claim 19 , the shift quantities satisfies following equation:
   shift quantity=[( i   —   cw+i   —   ccw )/2− i   —   cnt]× ( w+d )+ m  
 
 where, for the respective test pattern, ABS means absolute value of, i_cw is an index number of the light receiving element disposed at a location which first meets a vertex of the test pattern and i_ccw is an index number of the light receiving element disposed at a location which meets the opposite vertex of the test pattern, w is the width of each light receiving element, d is the width of an interval between each light receiving element, m is a margin and i_cnt is an index number of the light receiving element expected to be located at the center of the light receiving element. 
 
     
     
       21. The method of the color registration of  claim 20 , wherein determining the shift quantities of the respective test patterns further comprises, for a respective test pattern:
 determining whether the shift quantity continues to change while transferring the respective test patterns; and 
 calculating the shift quantity at a predetermined target location if the shift quantity of the respective test pattern is determined to continue to change. 
 
     
     
       22. An image forming apparatus that independently forms images of predetermined respective colors and forms a color image by overlapping the images of respective colors, comprising:
 an image forming unit to form respective test patterns for each color image on an image transfer path proportional to a corresponding format of a fed printing medium where the color image will be transferred; and 
 a color registration apparatus to independently form images of predetermined respective colors and to compensate a mis-registration between overlapped images of respective colors, including a detecting unit to detect a contour form and position information of respective test patterns for each color image formed on the image transfer path, and 
 a controller to compensate a mis-registration between overlapped images of respective colors based on data detected by the detecting unit, 
 wherein each test pattern comprises a first edge corresponding to a top edge part of the printing medium and a second edge corresponding to a side edge of the printing medium. 
 
     
     
       23. The image forming apparatus of  claim 22 , wherein the detecting unit comprises:
 a light source to radiate a light; and 
 a plurality of light receiving elements aligned to have a length larger than a maximum width of the printing medium permitted by the image forming apparatus, the plurality of light receiving elements extending across the image transfer path in a width direction of the test patterns; and 
 wherein interference of each test pattern is detected by the plurality of light receiving elements to determine a contour form, a skew quantity and a shift quantity of the test patterns. 
 
     
     
       24. The image forming apparatus of  claim 23 , wherein the plurality of light receiving elements have a same size with each other and are separated from each other by a constant interval. 
     
     
       25. The image forming apparatus of  claim 23 , wherein the plurality of light receiving elements have a same size with each other and are separated from each other by a constant interval. 
     
     
       26. The image forming apparatus of  claim 22 , further comprising a discriminating unit to discriminate whether there is a mis-registration and an extent of the mis-registration based on data detected by the detecting unit. 
     
     
       27. The image forming apparatus of  claim 26 , wherein the discriminating unit comprises:
 a memory to store the contour form information of respective test patterns; and 
 a counter to calculate a transfer time between the respective test patterns; 
 wherein the discriminating unit determines the color registration between the respective test patterns through comparing information of the respective test patterns detected by the detecting unit and the counter and information of the respective test patterns stored in the memory. 
 
     
     
       28. The image forming apparatus of  claim 27 , wherein each test pattern comprises:
 a first test pattern corresponding to a leading edge and opposites side edges at the leading edge of the printing medium; and 
 a second test pattern corresponding to a trailing edge and opposites side edges at the trailing edge of the printing medium. 
 
     
     
       29. The image forming apparatus of  claim 22 , further comprises a user interface unit to inform a user whether sizes of the respective test patterns accord with preset formats. 
     
     
       30. A method of creating an image by an image forming apparatus that independently forms images of predetermined respective colors and forms a color image by overlapping the images of respective colors, the method comprising:
 forming respective test patterns for each color image on an image transfer path proportional to a corresponding format of a printing medium where the color image will be transferred; 
 detecting contour form information of each test pattern; 
 creating an image having color registration compensated based on the detected contour form information of the fed printing medium, 
 wherein the detecting of the contour form information of each test pattern comprises: 
 radiating a light; 
 receiving the radiated light by a plurality of light receiving elements which are aligned to have a length longer than a maximum permitted width of the printing medium permitted by the image forming apparatus, the plurality of light receiving elements extending across an image transfer path of the printing medium; 
 at predetermined times during an existence of the respective test patterns, outputting a signal corresponding to the radiated light received by the plurality of light receiving elements; and 
 recognizing the contour form information of the respective test patterns using the output signal. 
 
     
     
       31. The method of image outputting of the image forming apparatus of  claim 30 , further comprising determining whether there is a mis-registration and an extent of the mis-registration based on the contour form of the respective test patterns. 
     
     
       32. The method of image outputting of the image forming apparatus of  claim 31 , wherein the determining whether there is a mis-registration comprises
 determining the sizes of the respective test patterns; 
 determining the skew quantities of the respective test patterns; and 
 determining the shift quantities of the respective test patterns. 
 
     
     
       33. The method of image outputting of the image forming apparatus of  claim 32 , wherein the determining the sizes of the respective test patterns comprises:
 calculating widths of the respective test patterns using an arithmetic operation having as variables a pass time of the respective test patterns, a location of individual light receiving elements of the detecting unit and a predetermined speed of the image transfer path. 
 
     
     
       34. The method of image outputting of the image forming apparatus of  claim 33 , wherein the determining the sizes of the respective test patterns comprises:
 determining a moving direction of the respective test patterns; 
 calculating widths of the respective test patterns from the output signal; and 
 wherein the method further comprises comparing the determined size of the text pattern with an expected size. 
 
     
     
       35. The method of image outputting of the image forming apparatus of  claim 34 , wherein the calculating the widths of the respective test patterns with the output signal satisfies following equation:
     P   width   =√X   2   +Y   2    
     X =ABS( i   —   cw−i   —   ccw )×( w+d )+ m  
 
     Y=f×V×T    
 where, for the respective test pattern, ABS means absolute value of, i_cw is an index number of the light receiving element disposed at a location which first meets a vertex of the test pattern and i_ccw is an index number of the light receiving element disposed at a location which meets an opposite vertex of the respective test pattern, w is the width of the light receiving element, d is a width of the interval between the light receiving elements, m is a margin that compensates to consider when the edge of each test pattern covers one light receiving element or the interval, f is a number of counts counted during an entering of the test pattern from the first entering of a vertex of the test pattern till the last entering of the other vertex of the test pattern, V is a moving speed of each test pattern, and T is a detecting period of the light receiving element. 
 
     
     
       36. The method of image outputting of the image forming apparatus of  claim 32 , wherein the plurality of light receiving elements are separated from their adjacent light receiving elements by a predetermined interval, and
 determining the sizes of the respective test patterns further comprises determining the position of at least one vertex of a leading edge of the respective test pattern within an interval between the adjacent light receiving elements when the at least one vertex of the respective test pattern enters the interval between the adjacent light receiving elements. 
 
     
     
       37. The method of image outputting of the image forming apparatus of  claim 36 , wherein the determining the position of at least one vertex of a leading edge of the respective test pattern within an interval between the adjacent light receiving elements comprises:
 storing a relationship of a skew quantity and an output pattern of a transition an output of the light receiving elements in a lookup table; 
 periodically storing sensed output values of the light receiving elements; 
 determining the skew quantity using the sensed output values of the light receiving elements and the relationship stored in the lookup table; 
 calculating a first line extending along the leading edge of each test pattern and a second line extending along a side edge of each test pattern; and 
 calculating the position of the at least one vertex of the leading edge of each test pattern from an intersection point of the first line and the second line. 
 
     
     
       38. The method of image outputting of the image forming apparatus of  claim 32 , wherein determining the skew quantities of the respective test patterns comprises for each test pattern:
 storing a count counted from a time when the test pattern is first detected until two opposite side edges of the test pattern is detected; 
 deciding whether the test pattern is skewed according to which light receiving element among the plurality of light receiving elements first detects the respective test patterns; 
 storing index values of the light receiving elements disposed at locations which first meet the first two vertexes of the test pattern; and 
 calculating the skew quantity based on the count and the stored index values. 
 
     
     
       39. The method of image outputting of the image forming apparatus of  claim 38 , the skew quantities satisfy following equations:
   Skew quantity=arctan( Y/X ) 
     X =ABS( i   —   cw−i   —   ccw )×( w+d )+ m  
 
     Y=f×V×T    
 where, for the respective test pattern, ABS means absolute value of, i_cw is an index number of the light receiving element disposed at a location which first meets a vertex of the respective test pattern and i_ccw is an index number of the light receiving element disposed at a location which meets the opposite vertex of the test pattern, w is the width of the light receiving element, d is the width of the interval between the light receiving elements, m is a margin that compensates to consider when the edges of the respective test patterns cover one light receiving element or the interval, f is a number of counts counted during an entering of the test pattern from the first entering of a vertex of the test pattern till the last entering of the other vertex of the test pattern, V is a moving speed of the respective test patterns, and T is a detecting period of the light receiving element. 
 
     
     
       40. The method of image outputting of the image forming apparatus of  claim 39 , wherein the determining the skew quantities of the respective test patterns further comprises:
 discerning whether the skew quantities continue to change while continuing to transfer the respective test patterns; and 
 estimating the skew quantities at a predetermined target location if the skew quantities are determined to continue to change. 
 
     
     
       41. The method of image outputting of the image forming apparatus of  claim 32 , wherein determining the shift quantities of the respective test patterns comprises, for a respective test pattern:
 determining which light receiving elements among the plurality of the light receiving elements are located at left and right portions of the leading edge of the respective test pattern. 
 
     
     
       42. The method of image outputting of the image forming apparatus of  claim 41 , the shift quantities satisfies following equation:
   shift quantity=[( i   —   cw+i   —   ccw )/2− i   —   cnt ]×( w+d )+ m  
 
 where, for the respective test pattern, ABS means absolute value of, i_cw is an index number of the light receiving element disposed at a location which first meets a vertex of the test pattern and i_ccw is an index number of the light receiving element disposed at a location which meets the opposite vertex of the test pattern, w is the width of each light receiving element, d is the width of an interval between each light receiving element, m is a margin and i_cnt is an index number of the light receiving element expected to be located at the center of the light receiving element. 
 
     
     
       43. The method of image outputting of the image forming apparatus of  claim 42 , wherein determining the shift quantities of the respective test patterns further comprises, for a respective test pattern:
 determining whether the shift quantity continues to change while transferring the respective test patterns; and 
 calculating the shift quantity at a predetermined target location if the shift quantity is determined to continue to change.